The proposed R01 is designed to empirically evaluate risk for serious conduct problems by focusing on early childhood precursors that may be particularly amenable to intervention. Acquiring skills to regulate negative emotional arousal is a critical developmental task of early childhood, but harsh parenting may restrict children's development of effective emotion regulation. During the toddler years, children's propensity towards negative emotional arousal and mothers' use of harsh parenting may evolve into mutually reinforcing, coercive cycles of interaction. Coercive interactions increase children's emotional arousal to levels that interfere with their efforts to effective emotional arousal, or strategies that reduce distress. Children's unregulated anger is hypothesized to predict more regulatory problems during interactions with siblings during the toddler years and later with peers upon entry into preschool. Theoretically, risk for clinically significant conduct problems (e.g., conduct disorder, externalizing problems, and oppositional defiant disorder) should be amplified when children enter preschool unable to control their negative emotions. The goal of this study is to identify specific process deficits that have direct application for preventions and interventions designed to deflect children from pathways leading to serious conduct problems. A longitudinal study of 160 2-year-old target children, their mothers, and their older sibling already enrolled in Head Start will be recruited. Target children will be followed annually from age 2 to age 4 (3 assessments). Very low income families have been found to be at increased risk for harsh parenting, but understudied in terms of their ability to socialize effective emotion regulation; they will be the focus of study. Both mothers' reports and observational assessments of target children's emotional reactivity, emotion regulation, and parenting will be used. Siblings will participate in observational, interactional activities to increase the ecological validity of the assessments and to measure children's regulatory capacities during exchanges involving an age-mate. Children's regulatory strategies observed during interactions with mothers are expected to correlate with their regulation during sibling exchanges and to later to their Head Start peers (age 4). Results from this study will fill critical gaps needed to increase the efficacy of intervention efforts designed to reduce the burden of serious conduct problems.